The Wall Street Mill in Joshua Tree National Park was a complete and operable gold ore crushing mill featuring late-19th Century two-stamp mill machinery.

The stamp mill building is framed with heavy timber and built on a downward sloping hillside to take advantage of gravity in the milling process. The roof and some of the exterior walls are covered with corrugated sheet metal, while some of the exterior walls have either vertical or horizontal wooden siding. At the top of the building a long wooden ramp supports the track of an ore tramway which carried ore from where it was unloaded from trucks to the top of the mill above the two-stamp Baker Iron Works crusher. A gasoline engine powered the mill.

The mill was built by Bill Keys, a local rancher, miner and character. In the 1940's, Keys was involved in a dispute with Worth Bagley over access to the Wall Street Mill. Keys shot and killed Bagley in 1943 and placed a stone commemorating the event with the inscription: "Here is where Worth Bagley bit the dust at the hand of W. F. Keys, May 11, 1943.